org.sonar.plugins.csharp.S2201.html Maven / Gradle / Ivy
Why is this an issue?
When you do not use the return value of a method with no side effects, it indicates that something is wrong. Either this method is unnecessary, or
the source code does not behave as expected and could lead to code defects. For example, there are methods, such as DateTime.AddYears, that don’t change the value of the input object,
but instead, they return a new object whose value is the result of this operation, and as a result that you will have unexpected effects if you do not
use the return value.
This rule raises an issue when the results of the following methods are ignored:
- LINQ
-
Pure methods
- Any method on build-in types
- Any method on Immutable
collections
Special cases:
- Although
string.Intern has a side effect, ignoring
its return value is still suspicious as it is the only reference ensured to point to the intern pool.
- LINQ methods can have side effects if they are misused. For example:
data.All(x =>
{
x.Property = "foo";
return true;
});
Such code should be rewritten as a loop because Enumerable.All<TSource> method should be used to
determine if all elements satisfy a condition and not to change their state.
Exceptions
This rule doesn’t report issues on invocations with out or ref arguments.
How to fix it
Code examples
Noncompliant code example
data.Where(x => x > 5).Select(x => x * x); // Noncompliant
"this string".Equals("other string"); // Noncompliant
data.All(x => // Noncompliant
{
x.Property = "foo";
return true;
});
Compliant solution
var res = data.Where(x => x > 5).Select(x => x * x);
var isEqual = "this string".Equals("other string");
foreach (var x in data)
{
x.Property = "foo";
}
Resources
Documentation
- Microsoft Learn -
PureAttribute
Class
- Microsoft Learn -
out
parameter modifier
- Microsoft Learn -
ref keyword
- Microsoft Learn -
String.Intern(String) Method
- Microsoft Learn - LINQ
- Microsoft Learn - build-in types
- Microsoft Learn - Immutable
collections
Articles & blog posts